Mr Buckley said his wife Wendy rang NRMA, thinking there must have been a mistake, as so many other people have done.

But she was told there was no mistake and that their house was in a "flood zone". Mr Buckley said his family had insured the house with NRMA for the seven years they had lived there. The house they lived in previously was also insured with NRMA.

But this renewal notice made them look elsewhere. That was when Mr Buckley found that other insurers were charging even more.

Of those who did respond, he said AAMI had quoted $16,000 to insure the house, while Allianz asked for $15,029.35.

"They were without any flood cover at all," Mr Buckley said. "They straight up said, 'we won't cover you for flood'.

A spokesman for AAMI refuted this claim, saying policies automatically included flood cover and customers were given the option of opting out of flood cover.

"This was the case in the quote this individual obtained - the initial quote, with flood cover, was $16,000," the spokesman said.

"The customer was given the option to opt out of flood cover, which would have reduced the premium by more than two-thirds."

The spokesman said the high premium was because "this property was in a high flood risk zone, not far from Byarong Creek".

No-one from Allianz responded to the Mercury's request for comment.

With the spate of residents reporting rises in the cost of their NRMA policies, the insurer was asked what had changed recently.

"At each customer's renewal, we take into account a range of factors to calculate their individual premium," a spokesman said.

"This includes information we have on all types of events including storm, earthquake, hail and bushfires.

"There are some customers who we believe have a higher risk to stormwater run-off than we had previously determined and, as such, we need to offer them a premium which reflects this risk."